1. Field of the Invention
The field of art to which this invention pertains is the solid bed molecular sieve separation of fatty acids. More specifically, the invention relates to a process for separating an oleic acid from a linoleic acid which process employs a molecular sieve comprising silicalite.
2. Background Information
It is known in the separation art that certain crystalline aluminosilicates can be used to separate certain esters of fatty acids from mixtures thereof. For example, in U.S. Pat. Nos. 4,048,205; 4,049,688 and 4,066,677 there are claimed processes for the separation of esters of fatty acids of various degrees of unsaturation from mixtures of esters of saturated and unsaturated fatty acids. These processes use adsorbents comprising an X or a Y zeolite containing a selected cation at the exchangeable cationic sites.
In contrast, this invention relates to the separation of certain fatty acids rather than fatty acid esters. We have discovered that a specific molecular sieve that exhibits selectivity for one unsaturated fatty acid with respect to another unsaturated fatty acid thereby making separation of such fatty acids by solid bed selective retention possible. Furthermore, we have discovered the enhanced effectiveness of specific displacement fluids at certain displacement conditions. In a specific embodiment our process is a process for separating oleic acid from linoleic acid. Substantial uses of fatty acids are in the plasticizer and surface active agent fields. Derivatives of fatty acids are of value in compounding lubricating oil, as a lubricant for the textile and molding trade, in special lacquers, as a waterproofing agent, in the cosmetic and pharmaceutical fields, and in biodegradable detergents.
We have discovered that silicalite, a non-zeolitic hydrophobic crystalline silica molecular sieve, is uniquely suitable for the separation process of this invention in that it first exhibits acceptance for a fatty acid with respect to a rosin acid, particularly when used with a specific displacement fluid, at specific displacement conditions, and does not exhibit reactivity with the free acids, and, second, it exhibits acceptance for oleic acid with respect to linoleic acid.